I've had this issue for as long as I can remember. when launching a game for the first time runs smoothly, however when I open a different game or just close and reopen the same game it runs at like 30fps lower. cant think of any reason for this problem. It's not cooling, since playing a game for multiple hours doesn't cause this problem. It's not that my pc is bad it happened in portal 1 not exactly a demanding game. though it seems to only affect steam games. and the only thing that fixes it for now is restarting my pc